Drill foe boeing metal



(No Model.)

F. BREARLEY 82: J. OVEREND.

DRILL FOR BORING METAL.

No. 535,939. Patented Mgr l g, 1895.

FFICEo nrniv'r FAIRBANK BREARLEY, OF BAILDON, AND JOSEPH OVEREND, OF FRIZING- HALL, ENGLAND.

DRILL FOR BORING METAL...

SPECIFICATION forming part Of Letters Patent No. 535,939, dated March 19, 1895.

Application filed November 9,1894. Serial No. 528,343- (ITo model.)

To aZZ whom it may concern.- a

Be it known that we, FAIRBANK BREARLEY, residing at Baildon, and Josnrfi OVEREND, residing at Frizinghall, near Bradford, York county, England, subjects of the Queen of Great Britain,have invented a certain new and useful Improvement in Straight-Grooved and spirally-Grooved or Twist Drills, of which the following description, together with the accompanying sheet of drawings, is a specification.

In the production of this class of drills for boring metal or other substances it is well known that the cutting edges at the outer ends of these drills must be formed at a certain angle to the axes of such drills to enable them to perform their functions in a thoroughly efficient and desirable manner. Moreover it is also equally as essential that these cutting edges should, on being sharpened or ground by the user, be maintained at this same desirable angle during the whole of the time that such drills are being worn down by use and repairs or sharpening. When these drills are being made, very little if any difficulty is experienced in forming their cutting edges as desired. However, when said cutting edges have had to be sharpened as when used in the Workshops and other places other than those in which they are manufactured then the real difficulty has presented itself and to overcome this heretofore, very expensive machinery has been brought into use which in addition to its cost, often entailed the outlay of requiring a highly skilled person to manage same. To avoid these disadvantages and to produce a drillwhich any ordinary artisan may as readily sharpen upon the usual grindstone or other abrading surface as he does the ordinary kind of drill thus dispensing with all expensive machinery and labor, is the object of our invention, and this object we attain as hereinafter described, reference being had to the accompanying sheet of drawings, in which Figures 1 and 3 are respectively side and transverse sectional views of a drill having spiral grooves formed in it, and well known as a twist-drill. Figs. 2 and at are similar views to Figs. 1 and 3 respectively, but. are illustrative of a straight grooved drill, our invention being applicable to both'wi'th equal advantages as will be understood from the following description.

Our invention consists of forming a series of lines or marks 0 upon the inner edge of the groove (1 formed in the drill e such said series of lines 0 being made at the proper angle to the axis (as indicated by the broken lines a b) of the drill 6 so that when the workman sharpens the cutting edge f he does so in the usual way, taking care to keep the cutting edge f always parallel with the indicating marks or lines c which are distributed over the whole length of said groove d in order to give such said guidance to the operative or user so long as the drill may last.

Since it is as desirable to have the cutting edge of straight drills as those of twist drills at the proper angle to the axial center it will be seen that our invention applies with equal advantages to both.

We are aware that parallel marks have been made on the periphery of a twist-drill to indicate the proper position of the inner corner of each lip in grinding; butsaid marks do not extend inwardly from the periphery as ours do, and therefore do not serve the same purpose, our marks extending from the periphery nearly to the center, so that each accurately guides the operator not only at the periphery but also between the periphery and center.

Having thus described our invention, what we claim is- A grooved drill having guiding lines or marks on the surfaces of its grooves, said lines being inclined relatively to the axis of the drill and parallel with its cutting edges f, substantially as and for the purposes specified.

FAIRBANK BREARLEY. JOSEPH OVEREND. Witnesses:

SAMUEL HEY, CLAUDE MEEKER. 

